Health Assessments of Koalas after Wildfire: A Temporal Comparison of Rehabilitated and Non-Rescued Resident Individuals

SIMPLE SUMMARY: Bushfires are a regular occurrence in the Australian landscape. The 2019/20 megafires were unprecedented in intensity and scale, impacting many native species. Koalas were particularly impacted by the fires, with many of those coming into care requiring extensive rehabilitation and treatment. Very little is known about the health parameters of rehabilitated koalas following their release and how these parameters may differ between individuals living in a burnt landscape compared to those in an unburnt landscape. This study tested haematological and serum biochemical parameters, chlamydial shedding and body condition scores of rehabilitated koalas and non-rescued residents living in burnt and unburnt habitats. All koalas received a health check 5–9 months post-fire and one 12–16 months post-fire. Rehabilitated koalas also received a health check when coming into care initially. While some variation in parameters was recorded, the majority of measurements in each koala group fell within the normal reference ranges, suggesting that resident and rehabilitated koalas were in good health at the time of release and when recaptured. These results show that koalas can be supported in burnt landscapes (provided there is adequate nutrition) and that the health of rehabilitated koalas is not compromised by returning them to burnt habitats. ABSTRACT: Many koalas (Phascolarctos cinereus) required rehabilitation after the 2019/20 Australian megafires. Little is known about how the post-release health of rehabilitated koalas compares to non-rescued resident koalas. We evaluated health parameters in rehabilitated koalas and resident koalas in burnt and unburnt habitat in southern New South Wales, Australia. Health checks were undertaken within six weeks of fire (rehabilitated group), 5–9 months post-fire and 12–16 months post-fire. Body condition improved significantly over time in rehabilitated koalas, with similar condition between all groups at 12–16 months. Rehabilitated koalas therefore gained body condition at similar rates to koalas who remained and survived in the wild. The prevalence of Chlamydia pecorum was also similar between groups and timepoints, suggesting wildfire and rehabilitation did not exacerbate disease in this population. While there was some variation in measured serum biochemistry and haematology parameters between groups and timepoints, most were within normal reference ranges. Our findings show that koalas were generally healthy at the time of release and when recaptured nine months later. Landscapes in the Monaro region exhibiting a mosaic of burn severity can support koalas, and rehabilitated koala health is not compromised by returning them to burnt habitats 4–6 months post-fire.